(1) Field of the Invention
The invention relates to ion exchange resins, methods of making ion exchange resins and their use in the removal of perchlorate from water.
(2) Description of the Related Art
Perchlorates occur both naturally and as a result of many manufacturing processes.
Industrial examples include potassium perchlorate and ammonium perchlorate which are commonly used in the pyrotechnics, aerospace and munitions industries. Most perchlorates are soluble in water and are long lasting once introduced into the environment. As a result of growing concerns regarding negative human health effects from exposure to perchlorates, many regulatory authorities have implemented stringent guidelines on perchlorate levels—particularly in connection with water.
One conventional method for removing perchlorate from a water source is treatment with a strong base ion exchange resin comprising a crosslinked styrene-divinylbenzene copolymer matrix with quaternary ammonium functionality. Such resins are described in US Patent Publication No. 2004/0256597, the entire contents of which are incorporated herein by reference. Commercial examples of such ion exchanges resins are available from The Dow Chemical Company and include: DOWEX™ 1 brand ion exchange resin, a strong base, gel-type resin functionalized with trimethyl amine; DOWEX™ NSR-1 brand ion exchange resin, a strong base, macroporous resin functionalized with triethyl amine; DOWEX™ PSR-2 brand ion exchange resin, a strong base, gel-type resin functionalized with tri-n-butyl amine; and DOWEX™ PSR-3 brand ion exchange resin, a strong base, macroporous resin functionalized with tri-n-butyl amine.
Other ion exchange resin promoted for use in perchlorate removal include: AMBERLITE™ PWA2 available from Rohm & Haas, CalRes 2103 and CalRes 2109 available from Calgon Carbon Corporations and A530E and A532E (advertised as “bi-functional”) available from Purolite. U.S. Pat. No. 6,059,975 describes the use of “bi-functional” (functionalized with two different types of tertiary amines) anion exchange resin for removal of pertechnetate and is incorporated herein by reference.